U.S., Seoul Plan Response in Case of North Korean Attack

By

Yuka Hayashi in Tokyo and

Julian E. Barnes in Washington

Updated March 26, 2013 5:02 a.m. ET

The U.S. and South Korea signed a military contingency plan to respond to possible attacks from North Korea, Washington's latest step to reassure its Asian ally as Pyongyang's increasing provocations and China's growing territorial ambitions fuel anxietiesin the region.

The announcement of the new accord was timed to the anniversary of the sinking of a South Korean warship, the Cheonan, on March 26, 2010, according to a U.S. defense...